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Z strengthening injection columns

Posted: Thu Mar 12, 2020 4:38 pm
by colbylippincott
I have been experimenting with a new (kind of) concept of making holes within a model, and filling them with plastic using the 3d printer to increase the z strength. The difference between what I am trying and what has been tried before is that I am using a pattern of overlapping holes (see attached) that are conical at the top and bottom. The advantages of this approach are:

1. The holes are fairly shallow, so the printer can easily fill them completely rather than trying to fill one long hole that spans the whole part.
2. The overlap between offset holes ensures that there are no layers that don't have the reinforcing column across them.
3. The pattern is easily scaled to fill whatever volume you want. I was thinking it could be implemented as an infill type.
4. The conical shape gives you a better bond because it physically locks the layers together, rather than just relying on the plastic bond
5. The conical shape also makes the overlap between columns transfer force better from one to the next.

If you were to implement this in ideamaker, I'm sure you could come up with some infill pattern that would include something that approximates these cavities, and make it faster to print and density scaleable like the other infills. I attached a few screenshots as an example of what it could look like. This would be an awesome feature that would get 3d printed parts to be more and more isotropic, closer to that of injection molded parts.

Here is the gcode if you want to print it yourself. However, make sure you only have one extruder, since for this test the nozzle does slightly lower into the hole while filling. For the final implementation in ideamaker, I think you can get away with not lowering the nozzle as long as the cavities are small enough. ... sp=sharing

Here is a video of me printing the gcode above: ... mLFXXRQ-3F

I am going to do some strength tests of this part vs. a 100% infill part with the same size. Stay tuned.

Re: Z strengthening injection columns

Posted: Thu Mar 12, 2020 7:53 pm
by colbylippincott
I broke the parts with the column reinforcement, and it looks like the filament didn't get down past the small section of the cavity. So I am going to try again with just straight columns. The cone shape may not matter at all in the end.

Re: Z strengthening injection columns

Posted: Sat Mar 21, 2020 1:07 pm
by zemlin
FWIW, I often print parts with through holes for reinforcement rods. I use steel.
I'll leave a straight hole in a part - for small holes I will ream them to size before driving in the rods. Larger holes I can generally use as-printed if I'm careful about the ID.

I'll put a small helix in the hole, or ribs ever 20mm or so on a long hole so the rod isn't a press fit over the full depth.